The Talvivaara/Terrafame multi-metal mining company is Europe’s largest nickel open cast mine, it is also known for the largest wastewater leakage in the Finnish mining history and a series of other accidents. In this paleolimnological study, influences of a recently constructed treated waste water discharge pipeline into Lake Nuasjärvi were investigated by analyzing past (pre-disturbance) and present community compositions of key aquatic organism groups, including diatoms, Cladocera and Chironomidae, along spatial (distance, water depth) gradients. In addition to defining ecological changes and impacts of saline mine waters in the lake, chironomids were used to quantitatively reconstruct bottom water oxygen conditions before and after the pipe installation (in 2015). The diatom and cladoceran communities, which reflect more the open-water habitat, showed only relatively minor changes throughout the lake, but a general decrease in diversity was observed within both groups. Chironomids, which live on substrates, showed more significant changes, including complete faunal turnovers and deteriorated benthic quality, especially at the sites close to the pipe outlet, where also chironomid diversity was almost completely lost. Furthermore, the reconstructed hypolimnetic oxygen values indicated a major oxygen decline and even anoxia at the sites near the pipe outlet. The limnoecological influence of the pipe decreased at sites located counter-flow or behind underwater barriers suggesting that the waste waters currently have location-specific impacts. Our study clearly demonstrates that whereas the upper water layers appear to have generally maintained their previous state, the deep-water layers close to the pipe outlet have lost their ecological integrity. Furthermore, the current hypolimnetic anoxia close to the pipe indicates enhanced lake stratification caused by the salinated mine waters. This study clearly exhibits the need to investigate different water bodies at several trophic levels in a spatiotemporal context to be able to reliably assess limnoecological impacts of mining.

Biomass is a dominant solid fuel type worldwide. Traditional biomass combustion leads to severe indoor and ambient environmental problems. Biomass pellet utilization in forced-draft gasifier stoves is regarded as an improved approach to these problems. Previous studies on forced-draft biomass stoves mainly considered average emission amounts and lacked details of the combustion properties and dynamic correlations between emissions and combustion. This study used a dynamic measurement system to test a typical forced-draft gasifier stove consuming wood pellets and maize straw pellets. Real-time fuel burning rate, that partly reflects the combustion performance, and CO, NOₓ and PM₂.₅ emission rates, over a whole combustion course, were monitored. In all tests, the burning rate rose to a high and stable level, and then sharply subsided. CO, NOₓ and PM₂.₅ emission rates varied across the combustion course. CO (NOₓ) emissions have a negative (positive) logarithmic linear relationship with burning rate, while no consistent relationship was observed for PM₂.₅ emission rate. The identified relationships between burning rate and pollutant emission rates suggest the possibility of estimating emission performance of forced-draft biomass pellet stoves based on combustion indicators, or vice versa.

The increasing release of engineered nanoparticles (NPs) from consumer products has raised great concerns about their impacts on biological wastewater treatment. In this study, the widely-used ZnO NP was selected as a model NP to investigate its impact on high-rate denitrifying granular sludge in terms of sludge properties and community structure. A hormesis effect was observed during short-term exposure, in which the specific denitrification activity (SDA) was stimulated by 10% at 1 mg L⁻¹ ZnO NPs, but inhibited by 23% at 5.0 mg L⁻¹ ZnO NPs. When continuously exposed to 2.5 mg L⁻¹ ZnO NPs, the nitrogen removal capacity of the denitrification reactor was nearly deprived within 15 days, and the relative abundance of the dominant denitrifying bacterium (Castellaniella) was decreased from 51.0 to 8.0%. Meanwhile, the dehydrogenase activity (DHA) and the content of extracellular polymeric substance (EPS) significantly decreased to 22.3 and 61.1%, respectively. Nevertheless, the presence of phosphate substantially weakened the adverse effects of ZnO NPs on the SDA, EPS, DHA and the relative abundance of functional genes even exposed to 6.25 mg L⁻¹ ZnO NPs, which was associated with the fact that the level of Zn(II) released from ZnO NPs was significantly reduced in the presence of phosphate. Therefore, the toxicity of ZnO NPs may be mainly attributed to the release of toxic Zn(II) and could be attenuated in the presence of phosphate. Overall, this study provided further reference and meaningful insights into the impact of engineered NPs on biological wastewater treatment.

Although fertilization plays an important role in determining the contents of soil dissolved organic matters or water-extractable organic matter (DOM, WEOM), knowledge regarding the dynamics, biodegradability, and microbial community shifts of WEOM in response to different fertilization treatments is very limited, particularly in rice–wheat cropping soil. Thus, in the present study, we performed biodegradation experiments using WEOM extracted from samples of soil that had been subjected to four different fertilization treatments: unfertilized control (CK), chemical fertilizer (CF), 50% chemical fertilizer plus pig manure (PMCF), and 100% chemical fertilizer plus rice straw (SRCF). UV spectrum and fluorescence 3D excitation–emission matrix analyses applied to investigate the chemical composition of WEOM revealed that all examined WEOMs were derived from microbial activity and the dominant portion comprised humic acid-like compounds. After the incubation, 31.17, 31.63, 43.47, and 33.01% of soil WEOM from CK, CF, PMCF, and SRCF treatments, respectively, were biodegraded. PMCF- derived WEOM had the highest biodegradation rate. High-throughput sequencing analyses performed to determine the microbial community before and after the incubation indicated that Sphingomonas, Bacillus, and Flavisolibacter were the predominant bacterial genera in the original inoculum derived from the four fertilization treatments. Following biodegradation, we observed that the dominant bacteria differed according to fertilization treatments: Curvibacter (43.25%) and Sphingobium (10.47%) for CK, Curvibacter (29.68%) and Caulobacter (20.00%) for CF, Azospirillum (23.68%) and Caulobacter (13.29%) for PMCF, and Ralstonia (51.75%) for SRCF. Canonical correspondence analysis revealed that, shifts in the microbial community were closely correlated with pH and specific UV absorbance at 254 nm. We speculated that the inherent traits of different WEOM and the properties of soil solutions under different fertilization treatments shaped the soil microbial community structure, thereby influencing the biodegradation of WEOM.

Understanding the chemical response and characteristics of bacterial communities in soil is critical to evaluate the effects of selenium (Se) supplement on plant growth and chromium (Cr)/Se uptake in Cr contaminated soil. The rhizosphere soil characteristics of pak choi (Brassica campestris L. ssp. Chinensis Makino) were investigated in soil contaminated with different levels and forms of Cr when supplemented with Se. Although inhibition of plant growth caused by Cr stress was not completely alleviated by Se, Cr content in plant tissues decreased in Cr(VI)120Se5 treatment (Cr(VI): 120 mg kg−1 soil; Se: 5 mg kg−1 soil) and its bioavailability in soil decreased in Cr(III)200Se5 (Cr(III): 200 mg kg−1 soil; Se: 5 mg kg−1 soil) treatment. Moreover, antagonism of Cr and Se on soil enzyme activities and bacterial communities were revealed. Notably, results of Cr(VI) reduction and Se metabolism functional profiles confirmed that bacterial communities play a critical role in regulating Cr/Se bioavailability. Additionally, the increases of Se bioavailability in Cr contaminated soil were ascribed to oxidation of Cr(VI) and reduction of Se reductases proportions, as well as the enhancing of pH in soil. These findings reveal that Se has the potential capacity to sustain the stability of microdomain in Cr contaminated soil.

For divalent metals, the Biotic Ligand Model (BLM) has been proven to be an effective tool to predict biological effects by taking into account speciation calculations and competitive interactions. Nonetheless, the BLM has only rarely been validated for trivalent metals (e.g. rare earth elements), and the potential competitive effects of protons has been understudied. In this paper, the short-term biouptake of indium (In), a trivalent metal that is a byproduct of zinc extraction and used in numerous applications including the semiconductor industry, was evaluated under controlled conditions. Short-term (i.e. 60 min) indium biouptake by Chlamydomonas reinhardtii was measured as a function of pH in order to verify the validity of the BLM. At a given pH, In biouptake could be well described by the Michaelis-Menten equation with conditional stability constants of KIn,pH=4.0 = 106.7 M-1, KIn,pH=5.0 = 108.6 M-1, KIn,pH=6.0 = 109.3 M-1 and maximum internalization fluxes of Jmax, pH=4.0 = 0.74 × 10−14 mol cm−2 s−1, Jmax, pH=5.0 = 1.60 × 10−14 mol cm−2 s−1, Jmax, pH=6.0 = 2.22 × 10−14 mol cm−2 s−1. Although several potential mechanisms for the role of pH were examined, the results were best explained by a competitive interaction of H+ with the In uptake sites using overall stability constants of logKIn = 9.76 M-1 and logKH = 15.66 M-1. Based on these results, pH will play a critical role in bioavailability measurements of the trivalent cations in natural waters.

Three-quarters of all marine debris (MD) consists of plastic, a reflection of their worldwide use, production and waste mismanagement. Data on MD distributions can improve our ability to effectively reduce debris that escapes onto shorelines and the ocean. In this study, the Matrix Scoring Technique (Marine Strategy Framework Directive Technical Group on Marine Litter) was applied as an approach to calculate the likelihood of single debris items originating from a series of potential sources. Factors considered were: identity and function of debris, beach location, influential activities, “mix” of debris found, presence of indicator items, and quantity of MD. The standing-stock (abundance and composition) of MD was investigated in two sandy beaches (Conceição and Porto Pim) of the Azores Archipelago (NE Atlantic) for the period 2012–2018. The results of this study show promise towards the implementation of a new classification method to determine beach debris sources in remote open-ocean areas.

Silver ions are among the predominant anthropogenic introduced pollutants in aquatic systems. As silver has effects on species at all trophic levels the community composition in aquatic habitats can be changed as a result of silver stress. The response of planktonic protists to environmental stressors is particularly important as they act both as producers and consumers in complex planktonic communities. Chrysomonad flagellates are of major interest, since this group includes heterotrophic, mixotrophic and phototrophic taxa, and therefore allows analysis of silver stress in organisms with contrasting nutritional strategies independent of a potential taxonomic bias. In a series of lab experiments, we compared the response of different trophic chrysophyte strains to low (5 μg L⁻¹), medium (10 μg L⁻¹) and high (20 μg L⁻¹) nominal Ag concentrations in combination with changes in temperature and light intensity (phototrophs), temperature and food concentration (heterotrophs), or a combination of the above settings (mixotrophs). All tested strains were negatively affected by silver in their growth rates. The phototrophic strains reacted strongly to silver stress, whereas light intensity and temperature had only minor effects on growth rates. For heterotrophic strains, high food concentration toned down the effect of silver, whereas temperatures outside the growth optimum had a combined stress effect. The mixotrophic strains reacted differently depending on whether their nutritional mode was dominated by heterotrophy or by phototrophy. The precise response pattern across all variables was uniquely different for every single species we tested. The present work contributes to a deeper understanding of the effects of environmental stressors on complex planktonic communities. It indicates that silver will negatively impact planktonic communities and may create shifts in their composition and functioning.

Suffered from serious air pollution, Beijing, the capital of China, has implemented multiple measures to reduce the discharge of PM₂.₅ (particulate matter with aerodynamic diameters of less than 2.5 μm). The average annual PM₂.₅ concentration of Beijing has shown a continued decline in recent years. However, the improvement was not obvious during the heating season, which had heavier pollution than the non-heating season. Analyzing the spatial distribution of PM₂.₅ concentrations during heating and non-heating seasons, as well as their spatial differences, is believed to benefit the study of spatial-temporal variation of air pollution and provide scientific reference for the control of air pollution in Beijing. In this study, land use regression (LUR) model was employed to simulate the spatial distribution of PM₂.₅ concentrations in Beijing during heating and non-heating seasons in 2015. The spatial distribution of the concentration difference between heating and non-heating seasons was analyzed, and the influencing factors were also examined. The results showed that: (1) PM₂.₅ concentrations during heating and non-heating seasons, as well as their differences, were clearly at a maximum in the south and east of Beijing and at a minimum in the north and west; (2) the area with the biggest concentration difference was situated in a suburban area to the south and east, as well as in outer suburbs to the southeast and northwest; and (3) wind speed, area of transport land and industrial-mining-warehouse land were the main influence factors for the PM₂.₅ concentration difference in the central, eastern and southern area. Heating activity was not the only cause for the increased PM₂.₅ concentration during the heating season, vehicle emission, industrial discharge and regional transport of pollutants also played varied roles in PM₂.₅ pollution in different area.

Volatile organic compounds (VOCs) are an important factor affecting ambient air quality, and furniture production is one of the important sources of VOC pollution. High VOC concentrations have adverse effects on the environment and worker welfare in furniture factories. In order to control VOC emissions in a furniture workshop, the VOC species and concentration distributions were examined. Qualitative analysis of VOC species was carried out by headspace gas chromatography/mass spectrometry. The results showed that VOCs from a furniture workshop were mainly 12 substances including acetate, toluene, and xylene compounds. The heights and representative positions of VOCs released during the coating process were determined, and the results showed that VOC concentrations depended on environmental and height factors. The concentration of VOCs decreased with increasing altitude and reached a maximum concentration at 0.4 m above the ground. Because the concentration of VOCs varied with temperature, humidity, air pressure, and amount of spray paint, this paper established functional relationships between VOC concentrations and temperature, humidity, air pressure, and amount of spray paint. These results provide a theoretical basis for furniture workshops to automatically monitor and control VOCs.VOCs from the furniture workshop were mainly composed of 10 substances including acetate, toluene, and xylene compounds.